From 5a52bfff425556b9b61b92ddf933640c780e88d8 Mon Sep 17 00:00:00 2001
From: Robert Wesner <robert@wesner.io>
Date: Mon, 9 Nov 2026 11:08:31 +0100
Subject: [PATCH] Add support for invokedynamic string concatenation.

---
 .../net/lenni0451/authhook/UrlRedirector.java | 48 ++++++++++++++-----
 1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/Agent/src/main/java/net/lenni0451/authhook/UrlRedirector.java b/Agent/src/main/java/net/lenni0451/authhook/UrlRedirector.java
index c9674e0..4f6db2e 100644
--- a/Agent/src/main/java/net/lenni0451/authhook/UrlRedirector.java
+++ b/Agent/src/main/java/net/lenni0451/authhook/UrlRedirector.java
@@ -21,6 +21,7 @@
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.tree.AbstractInsnNode;
 import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.InvokeDynamicInsnNode;
 import org.objectweb.asm.tree.LdcInsnNode;
 import org.objectweb.asm.tree.MethodNode;
 
@@ -59,21 +60,33 @@ public byte[] transform(final ClassLoader loader, final String className, final
             boolean modified = false;
             for (MethodNode method : node.methods) {
                 for (AbstractInsnNode insn : method.instructions) {
+                    String str = null;
                     if (insn instanceof LdcInsnNode && ((LdcInsnNode) insn).cst instanceof String) {
-                        final LdcInsnNode ldc = (LdcInsnNode) insn;
-                        String str = (String) ldc.cst;
-                        for (String url : URLS) {
-                            if (str.startsWith(url)) {
-                                str = str.substring(url.length());
-                                str = this.targetAddress + "/" + this.secretKey + "/" + Base64.getUrlEncoder().encodeToString(url.getBytes(StandardCharsets.UTF_8)) + str;
-                                ldc.cst = str;
-
-                                modified = true;
-                                System.out.println("Redirected '" + url + "' in class '" + node.name + "' method '" + method.name + "'");
-                                break;
-                            }
+                        str = (String) ((LdcInsnNode) insn).cst;
+                    } else if (insn instanceof InvokeDynamicInsnNode) {
+                        final InvokeDynamicInsnNode indy = (InvokeDynamicInsnNode) insn;
+
+                        if (indy.bsm.getOwner().equals("java/lang/invoke/StringConcatFactory")
+                            && indy.bsm.getName().equals("makeConcatWithConstants")
+                            && indy.bsmArgs.length > 0
+                            && indy.bsmArgs[0] instanceof String) {
+                            str = (String) indy.bsmArgs[0];
                         }
                     }
+
+                    if (str == null) continue;
+
+                    final String redirected = this.redirectUrl(str);
+                    if (redirected == null) continue;
+
+                    if (insn instanceof LdcInsnNode) {
+                        ((LdcInsnNode) insn).cst = redirected;
+                    } else {
+                        ((InvokeDynamicInsnNode) insn).bsmArgs[0] = redirected;
+                    }
+
+                    modified = true;
+                    System.out.println("Redirected URL in class '" + node.name + "' method '" + method.name + "'");
                 }
             }
             return modified ? this.write(node) : null;
@@ -95,4 +108,15 @@ private byte[] write(final ClassNode node) {
         return writer.toByteArray();
     }
 
+    private String redirectUrl(final String str) {
+        for (String url : URLS) {
+            if (str.startsWith(url)) {
+                return this.targetAddress + "/" + this.secretKey + "/"
+                    + Base64.getUrlEncoder().encodeToString(url.getBytes(StandardCharsets.UTF_8))
+                    + str.substring(url.length());
+            }
+        }
+        return null;
+    }
+
 }